Bump python-multipart in /functions/github-webhook-app-update

Bumps [python-multipart](https://github.com/Kludex/python-multipart) from 0.0.9 to 0.0.18.
- [Release notes](https://github.com/Kludex/python-multipart/releases)
- [Changelog](https://github.com/Kludex/python-multipart/blob/master/CHANGELOG.md)
- [Commits](Kludex/python-multipart@0.0.9...0.0.18)

---
updated-dependencies:
- dependency-name: python-multipart
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

functions/github-webhook-app-update/requirements.txt

@@ -20,7 +20,7 @@ pydantic==2.7.1
 pydantic_core==2.18.2
 Pygments==2.18.0
 python-dotenv==1.0.1
-python-multipart==0.0.9
+python-multipart==0.0.18
 PyYAML==6.0.1
 rich==13.7.1
 shellingham==1.5.4